Tap setter



A ril 16, 1963 s. A. DOUGLAS 3,085,321

TAP SETTER Filed Nov. 5, 1958 2 Sheets-Sheet 1 April 16, 1963 s. A.DOUGLAS TAP SETTER 2 Sheets-Sheet 2 Filed Nov. 5, 1958 United StatesPatent 3,085,321 TAP SETTER Samuel Arthur Douglas, Endicott, N.Y.,assignor to General Precision Inc., Wilmington, DeL, a corporation ofDelaware Filed Nov. 5, 1958, st. No. 772,073 7 Ciainis. (Cl. 292tl3)This invention relates to instruments for assembling electricalappliances, and, more particularly, to devices for applying taps toassembled potentiometers.

Resistors, both fixed and variable, are well known electrical componentswhich have been in use almost as long as electricity itself has beenutilized. Originally resistors were fashioned haphazardly from anysubstance which would produce the desired eifect, and their use wasprimarily for rough adjustment of the current flow or potential in acircuit. As the science of electricity developed, so did the need formore accurate resistors and for more effective and improved methods ofmanufacturing them.

As new resistor compositions were developed, they were used for variableas well as fixed resistors, for the uses of components in which theresistance could be varied over a range of values were growing. However,it was not until the use of analog computers for both training andcontrol became widespread that the demand for potentiometers of greataccuracy and precision grew to great proportions. With the presentemphasis upon electrical and electronic training aids and controlsystems for operating everything from garage doors to guided missiles,the use of potentiometers has become great. And the potentiometersrequired for modern appliance-s must be precision instruments.

Since the growth of resistors has been of both the fixed and thevariable types, it has become evident that the combining of bothfunctions in a single device would greatly increase its versatility andaid in the reduction in the size and complexity of circuits in which itwas used. This is especially true of large machines such as modernaircraft training systems. The simulation on the ground of theoperations of the multitude of parts in an aircraft in response toactions of a pilot trainee requires analogue computers which utilizelarge numbers of both fixed and variable resistors. For accurate andlifelike simulation, precision components must be used, and the cost ofsuch equipment, as well as the space required thereby, is great.

In an eifort to overcome these problems, potentiometers of high accuracyhave been developed. These potentiometers are designed to be stacked andto operate in ganged groups to standardize their production and soreduce the cost of manufacture and the space requirements. In addition,taps can be applied to the potentiometers to provide fixed resistancevalues and eliminate the need for many fixed resistors. However, thetaps must be applied to the potentiometer with an accuracy of the sameorder as that of the original potentiometer, and the taps should becapable of rapid and simple replacement by equipment that can be easilyused in the field as well as in the manufacturing plant. By such means,the number of different resistors required by many installations can bematerially reduced, reducing the size of inventories and of necessarystorage space. Also, resistance values could then be changed withoutexpensive dismantling of complex equipment and the replacement ofexpensive parts.

It is an object of this invention to provide a new and improved devicefor applying taps to electrical appliances.

It is another object of this invention to provide a new and improvedportable machine for rapidly and accurately applying taps to variableresistor elements.

It is a further object of this invention to provide a new and improvedapparatus for applying removably positioned taps and potentiometers andfor electrically checking the positioning of the taps so applied.

Further objects and advantages of this invention will become apparent asthe following description proceeds, which description should be taken inconjunction with the accompaying drawings, in which:

FIG. 1 illustrates, in perspective, the device of this invention;

FIG. 2 is a sectional view of the apparatus illustrated in FIG. 1;

FIG. 3 is a plan view of a portion of the device shown in FIG. 1;

FIG. 4 is an elevational view of a portion of the device of FIG. \1shown enlarged; and

FIG. 5 is a perspective view of portions of the device illustrated inFIG. 4.

Referring now to the drawings in detail, the reference character 11designates a generally circular base which supports a centrally splitring portion 12 adapted to carry a potentiometer 41 to which taps are tobe applied. The ring '12 is split at one side 13, and the portions oneither side of the split 13 comprise legs 15 and 16 through which isthreaded a clamping set screw 14. An annular portion 1'7 is supported bythe base 11 for rotation in a depression formed therein. A base portion18 of an upright support member 23 is mounted on the annular portion 17,and the annular portion 17 is surrounded by a ring-shaped scale member19 which is affixed to the base 11 by means of screws 21. A knurl headedscrew 22 is threaded into the base 11 through the scale 19 for clampingthe ring portion 17 into any fixed position.

The upright support member 23 carries on its upper portion an L-shapedlever arm 24 having a cylindrical plunger member 25 fastened to itsupper horizontal portion. Surrounding the cylindrical plunger 25 is acoil spring 26 so arranged as to maintain the lever arm 24 in a raisedposition. The lower end of the vertical portion of the lever arm 24-carries a tap setting member 27 having a spring portion 28 therein. Thelever arm and the tap carrying assembly are supported in an appropriategroove in the support member 23 and are contained therein by a faceplate 20 removably attached thereto. An arm 31 having a cylindricalhandle portion 32 is rotatably supported on one side of the base member23 by means of a pivot screw 33. The extreme end of the arm 31 has anotch 34 fashioned therein with diver-gent outer portions for receivingthe pin projection of a potentiometer wiper arm. A wrench 38 is used foradjusting the clamping set screw 14 to fixedly attach or remove apotentiometer 41 to the apparatus, and a wooden cylinder 39 havingtapered end portions is used to adjust or remove the taps from thepotentiometer.

As shown more clearly in the enlarged view of FIG. 5, the end portion 27of the lever 24 comprises a hollow body portion 36 which tapersoutwardly and upwardly from a knife edge to a shoulder portion 37. Theinner vertical surface of the body 36 has a keyhole slot 35 cut thereinthrough which a portion of the spring member 28 can be seen. Shown inFIG. 2 is the potentiometer comprising a housing 41 having a resistanceelement 42 mounted therein about the inside circumference of thehousing. The base member 43 of the potentiometer has an upwardlyprojecting portion 44 about which is the U-shaped portion 45 of a fixedtap. At one end of the fixed tap adjacent the resistance element 42 is asharp, pointed contact element 46, and a connecting wire (not shown) isfastened to the opposite end 47 of the tap.

within the housing.

Mounted on a shaft (not shown in FIG. 2) which passes through thehousing 41 is a wiper arm 38 which carries the sliding contact elementsof the potentiometer. Also carried by the potentiometer housing 41,although not shown herein, is a device to which the individual fixed tapand the contact elements of the potentiometer may be connected forconnection to external devices. The pin 49, at one end of the contactarm 43, is shown in FIG. 2 in operative relation to the notch 34 in theend of the arm 31. Also shown in FIG. 2 is the manner in which thecylindrical plunger is attached to the arm 24 and in which the coilspring 26 surrounds the cylindrical plunger 25 and is inserted in acylindrical opening 51 in the upright support 23.

In operation, the potentiometer housing 41 is mounted in the split ring12 such that, with the index 52 on the annular portion 17 at the zeroposition, one end of the resistant element 42. of the potentiometer isdirectly under the V-notch in the spring member 28. In this position theclamping set screw i4 is rotated by means of the wrench 38 to lock thepotentiometer into position. The knurled screw 22 is released so thatthe annular portion 17, the upright support 2 3 and the associatedelements carried thereby may be rotated with respect to thepotentiometer 41 and with the scale :19. A tap is then inserted betweenthe spring member 28 and the back portion 27 of the nose portion 36,with the pointed contact element 46 in the keyhole slot 35. The spring28 releasably holds the tap in position against the back wall 2'7 of thenose portion 36. The annular portion 17, together with the uprightsupport 23, is then rotated until the index 52 indicates the angularposition at which a tap is to be inserted in the potentiometer, and theknurled headed screw 22 is hand tightened to hold the rotating portionin that position. The upper portion of the lever arm 24 is thendepressed against the action of the spring 25 to force the tap into thepotentiometer housing so that the U-shaped portion 45 of the tapresiliently clamps around the projection 44 The pointed contact element46 then makes contact with the resistance element 42. When the lever arm24 is released, it springs back into its uppermost position and thespring member 28 releases the tap so that it remains in thepotentiometer housing.

Additional taps may be readily inserted by releasing the locking screw22 and rotating the annular portion 17 and the upright support 23 to anew position as indicated by the index mark 52. A second tap may then beinserted between the springzfi and the nose portion 56 and inserted intothe proper position in the potentiometer 41. The scale 1% is calibratedin one degree markings and is positioned around the outer periphery ofthe base 11 to pro vide greater accuracy in setting. It is possible toset a removable tap within one degree of the desired position in apotentiometer.

To ensure that the tap has been located in the position in which it issupposed to be, it may now be checked by the same device which appliedthe tap initially used in conjunction with a resistance measuringinstrument. With the potentiometer 41 still clamped in its initial zeroposition, the rotatable contact arm 48 of the potentiometer is rotateduntil the pin portion 49 is directly under the notch 34 in the arm 31.The arm 31 is then rotated about the axis provided by the screw 33 toengage the pin 49. The lock screw 22 is released and the annular portion17 and the upright support member 23 are rotated until the index mark 52indicates the position at which the initial tap was applied to thepotentiometer. Resistance readings are then made between the end of thepotentiometer and the lead from that particular tap, and, if necessary,the tap is moved slightly by means of the tapered wooden cylinder 39until a null reading is indicated by the meter. This procedure isrepeated for each tap so applied to the potentiometer until all of thetaps have been situated accurately within the potentiometer. By thismeans it is possible to adjust the electrical positions of the tapsslight- 1y at any time to compensate for manufacturing variations andmaintain with precision relative resistance values between the ends ofthe resistance element 42 and the fixed taps 46.

Since the tap elements are held into position by the friction exertedagainst the projecting portion 44 of the potentiometer housing and theU-shaped portion 45 of the tap itself, the taps may be readily removedby prying loose with the tapered cylindrical member 39 for emplacementin a different location or for adjustment purposes. In this manner thenecessary inventory which must be carried by a laboratory or other suchorganization which may require periodically changing resistance elementsmay be greatly reduced. The potentiometer 41 may be standardized andproduced with great accuracy in large numbers and in a Wide variety ofsizes, and the application of the taps accurately by the deviceillustrated and described herein may produce an infinite number ofchangeable resistance relationships to produce versatile equipment.

This specification has described a new and elfective device for rapidlyand easily removably applying fixed taps to potentiometers and othersuch portable electrical appliances. Since this description may suggestto those skilled in the art other forms which this invention may take,it is intended that this invention be limited only by the scope of theappended claims.

What is claimed is:

1. Apparatus for applying attachments to electrical appliances, saidapparatus comprising a base of substantially circular shape, an annularmember rotatably mounted on said base, the plane of said annular memberbeing parallel to the plane of said base, a support member perpendicularto the plane of said annular member and mounted thereon, means attachedto said base in the center portion of said annular member for clam-pingan appliance into a fixed position in which its axis coincides with theaxis of rotation of said annular member, vertically movable meansmounted on said support member and biased to an upward position, aresilient holding member supported at the lower end of said verticallymovable means for removably holding an attachment, and annular scalemeans mounted about the outer periphery of said base member forindicating the relative positioning of said vertical support means andan appliance clamped on said base whereby said attachment may beaccurately applied to a preselected location on an appliance supportedin said clamping means.

2. Apparatus for applying attachments to electrical appliances, saidapparatus comprising a generally circular base having an annulardepression in a plane surface thereof, said depression being concentricwith said base, a ring seated in said depression and rotatable about itscenter, an upright support mounted on said ring over a portion thereof,a lever mounted on said upright support for sliding vertical movement,means for biasing said lever into its uppermost position, means at thelower end of said lever for removably carrying an attachment to beapplied to an appliance, and clamp means attached to said base forremovably clamping an appliance to which attachments are to be appliedin a position in which its axis coincides with the axis of rotation ofsaid ring.

3. Apparatus for applying attachments to electrical appliances, saidapparatus comprising a base having an annular depression in an uppersurface thereof, a ring slidably seated in said depression for rotationabout the center of said ring, releasable means for holding the ring ina desired position, a support member mounted on said ring, clamp meansaflixed to said base to removably clamp an appliance in a fixed positionin which its axis coincides with the axis of rotation of said ring,means carried by said support member for applying an attachment to anappliance held in said clamp means, and a scale surrounding said ringfor use in determining the circumferential location on said appliance atwhich an attachment will be applied by said means carried by the supportmember.

4. Apparatus for applying removable, fixed taps to a potentiometer, saidapparatus comprising a base, a ring rotatably mounted at the uppersurface of said base, clamp means attached to said base within said ringwhereby said ring rotates about said clamp means, a support memberperpendicular to the plane of said ring and mounted thereon, verticallymovable means mounted on said support member and biased to an upwardposition, a resilient holding member supported at the lower end of saidvertically movable means for removably holding a tap to be applied, saidclamp means clamping a potentiometer in operative relation to saidholding means, an annular scale about the outer circumference of saidring for indicating the relative circumferential position of saidholding means with respect to a potentiometer in the clamp means, andreleasable lock means for temporarily locking the ring and the holdingmeans in a desired circumferential position.

5. A device for applying taps to potentiometers of the type whichcomprise a housing having a resistance ele ment mounted therein aboutthe inside circumference thereof and a tap-supporting rail membersubstantially concentric with said resistance element over Which atleast one tap is adapted to be engaged, the end of said tap remote fromsaid rail member engaging said resistance element when said tap isclampingly disposed over said rail member, said device comprising: abase; support means mounted on said base; potentiometer holding meansmounted on said base; tap carrying means mounted on said support means,said support means being rotatable about the axis of a potentiometermounted in said potentiometer holding means; means for fixing said tapcarrying means at any desired angular position about said potentiometeraxis; and means mounted on said support means for holding the wiper armof said potentiometer fixed with respect to said tap carrying means.

6. A device for applying taps to potentiometers of the type whichcomprise a housing having a resistance element mounted therein about theinside circumference thereof and a tap-supporting rail membersubstantially concentric with said resistance element over which atleast one tap is adapted to be engaged, the end of said tap remote fromsaid rail member engaging said resistance element when said tap isclampingly disposed over said rail member, said device comprising: abase; vertical support means mounted on said base; potentiometer holdingmeans mounted on said base; vertically operable, upwardly spring-biasedtap carrying means mounted on said support means, said tap carryingmeans being rotatable about the axis of a potentiometer mounted in saidpotentiometer holding means at such a radius from said axis as to remainalways above a tap mounting rail in said potentiometer; means for fixingsaid tap carrying means at any desired angular position about saidpotentiometer axis; and means pivotally mounted on said support meansfor holding the wiper arm of said potentiometer fixed with respect tosaid tap carrying means.

7. Apparatus for applying taps to electrical potentiometers of the typewhich comprise a housing having a resistance element mounted thereinabout the inside circumference thereof and a tap-supporting rail membersubstantially concentric with said resistance element over which atleast one tap is adapted to be engaged, the end of said tap remote fromsaid rail member engaging said resistance element when said tap isclampingly disposed over said rail member, said apparatus comprising: abase having an annular depression in the top surface thereof, a ringslidably seated in said depression, a vertical support mounted on saidring, a lever vertically movably supported by said support, means forbiasing said lever to its uppermost position, a tap carrier mounted onthe lower end of said lever, and means affixed to said base for clampinga potentiometer in a position to receive a tap when said lever is moveddownwardly.

References Cited in the file of this patent UNITED STATES PATENTS159,904 Coombe Feb. 16, 1875 659,626 Pomeroy Oct. 9, 1900 1,665,926 HullApr. 10, 1928 2,094,517 Andreoli Sept. 28, 1937 2,172,847 Nydegger Sept.12, 1939 2,279,611 Barnhardt Apr. 14, 1942 2,341,176 Buehrig Feb. 8,1944 2,360,115 Droll Oct. 10, 1944 2,418,209 Watts Apr. 1, 19472,865,089 Machian Dec. 23, 1958 2,872,723 Sorber Feb. 10, 1959 2,873,509Levine et a1. Feb. 17, 1959 2,873,516 McCain et al. Feb. 17, 1959

1. APPARATUS FOR APPLYING ATTACHMENTS TO ELECTRICAL APPLIANCES, SAIDAPPARATUS COMPRISING A BASE OF SUBSTANTIALLY CIRCULAR SHAPE, AN ANNULARMEMBER ROTATABLY MOUNTED ON SAID BASE, THE PLANE OF SAID ANNULAR MEMBERBEING PARALLEL TO THE PLANE OF SAID BASE, A SUPPORT MEMBER PERPENDICULARTO THE PLANE OF SAID ANNULAR MEMBER AND MOUNTED THEREON, MEANS ATTACHEDTO SAID BASE IN THE CENTER PORTION OF SAID ANNULAR MEMBER FOR CLAMPINGAN APPLIANCE INTO A FIXED POSITION IN WHICH ITS AXIS COINCIDES WITH THEAXIS OF ROTATION OF SAID ANNULAR MEMBER, VERTICALLY MOVABLE MEANSMOUNTED ON SAID SUPPORT MEMBER AND BIASED TO AN UPWARD POSITION, ARESILIENT HOLDING MEM BER SUPPORTED AT THE LOWER END OF SAID VERTICALLYMOVABLE MEANS FOR REMOVABLY HOLDING AN ATTACHMENT, AND ANNULAR SCALEMEANS MOUNTED ABOUT THE OUTER PERIPHERY OF SAID BASE MEMBER FORINDICATING THE RELATIVE POSITIONING OF SAID VERTICAL SUPPORT MEANS ANDAN APPLIANCE CLAMPED ON SAID BASE WHEREBY SAID ATTACHMENT MAY BEACCURATELY APPLIED TO A PRESELECTED LOCATION ON AN APPLIANCE SUPPORTEDIN SAID CLAMPING MEANS.